class_docstr: Mutate the leaf node (i.e., ValueChoice) of parameter choices.
  
  Should be used together with :class:`ParameterChoiceMutator`.
code: def __init__(self, candidates: List[Any], label: str):
      super().__init__(label=label)
      self.candidates = candidates
  
imports: from __future__ import annotations
  from typing import Any, List, Tuple, Dict, Iterable, cast
  from nni.mutable import MutableExpression, Categorical, frozen_context, label_scope
  from nni.nas.space import Graph, GraphModelSpace, Node, StationaryMutator, Mutator
  from nni.nas.space.graph_op import Cell
label_desc: Use image node_id 1 to create a new ParameterChoiceLeafMutator object from inherited base classes: StationaryMutator with example: obj = ParameterChoiceLeafMutator(candidates, label)